The goal of this project is to evaluate the effectiveness of an intensive AIDS prevention program to eliminate and/or reduce risk acts that will transmit the HIV virus from 540 HIV+ youths aged 14-20 from three AIDS epicenters (Los Angeles [LA], New York [NY], and San Francisco [SF]). Changes in sexual and substance abuse risk acts will be monitored over 18 months (assessed at intake, 2, 4, 6, 12, and 18 months) as youths are randomly assigned within each site to one of the two intervention conditions designed on the AIDS Risk Reduction Model (ARRM): 1) a core module of 15-20 hours of AIDS prevention reflecting the current best intervention practice; or 2) three modules (the core module, a specialized HIV+ module, and a booster module) of 15-20 hours each, tailored specifically for HIV+ youths. There are few guidelines on how to adopt the ARRM for HIV+ youths, as the data are very limited. Therefore, prior to initiating the prevention trial, an ethnographic study will document the physical, social, and interpersonal contexts that characterize the lives of HIV+ youths and the impact of seropositivity on HIV+ youths as we observe how youths learn to adapt to their serostatus over one year. Differential effectiveness will be examined as a function of three sets of mediating factors: background characteristics (e.g., gender, sexual orientation), acquisition of the skills and norms taught in the intervention, and site. Finally, we will examine whether reductions in HIV risk acts are associated with changes in physical health and other problem behaviors (e.g., school and conduct problems, suicidality).